4,000+ fps How Long to Burn the Barrel

My 220 swift went from 5/16" groups when new to right over 1" groups at 1600 rounds. Most of these 1600 rounds were shot prairie dog killing (about as abusive as anything). This rifle shot best .010" off the lands and I could no longer reach this point due to throat erosion.

there is a little more to the equation than just going 4000 fps at the muzzle. Case design and throat design are also major factors to this as well. Longer necks verses shorter necks are well known to promote a longer barrel life. Even certain types of powders will errode a throat quicker than others will. Plus the shoulder angle has a lot to do with throat life. Then there's also the idea that certain powders produce a higher range of heat during their burn than others do (4064 comes to light). Huge cases that are very overbore tend to also blast the barrel like a sand blaster with unburnt powder granules.
gary

1 to 1.5 MOA, 10,000 rounds. These are the typical numbers for US 30 caliber service rifles, the M1 and M14. I would imagine the 5.56 NATO would be close to the same, but have no experience or other info to go on.

Double the powder charge weight for a given bore and barrel life goes down to 1/4 as many shots.